Thermostatic control system



Feb. 10, 1931. A. CROSSLEY 1,791,804

THERMOSTATI C CONTROL SYSTEI Filed May 27, 1927 II 'F 1 IN V EN TOR.

jag/fed TOS$Z% Patented Feb. 10, m

UNITED STATES PATENT OFFICE mm CBOSSLEY, WASHINGTON, DISTRICT A8816 'JlO runner. TELEGRAPH FOB-NIL mlmos'rarrc common stem Application ma lay :1, 1027. Serial Io. 194,797.

My invention relates broadly. to electrical control circuits and more particularly to a thermostatic control circuit capable of controlling the 0 ration of an electrical circuit over a limite and predetermined tempera ture range.

One of the objects of m invention is to provide an electron tube t ermostatic control circuit having means for eflc'ecting the a opening or closing of an electrical circuit in accordance with a predetermined temperature condition.

' Another object of my invention is to provide a thermostatic electron tube control circuit that is responsive to slight changes in temperature for closing or opening an electrical circuit.

My invention finds particular application in piezo electric crystal control circuits where an it is necessary to maintain the piezo electric element at a constant frequency. The circuit arrangement of my invention is capable of holding the temperature of a crystal container to within less than one-tenth of a 5 de ee centigrade of a specified temperature.

l y invention will be more fully understood from the specification hereinafter following by reference to the accompanying drawings in which:

Figure 1 is a side elevation of one construction of a thermostatic control device emploged in the circuit of my invention; Fig. 2 s ows diagrammatically the arrangement of the thermostatic control circuit of my invention; and Fig. 3 shows the application of the control circuit of my invention to a piezo electric crystal controlled transmitter circuit.

In obtaining the fine temperature adjust ment of the apparatus of my invention, I provide a mercury column or a bi-metallic expansion member either of which-has a multipl ing feature. The mercury column or capi lary tubing should be of as small a 4i bore as possible and the mercury base bulb should be relatively large in order that a small change in temperature will cause a large change in height'of the mercury col umn. The bi-metal expansion member ma consist of a spiral strip and a long arm with suitable contact members thereon for cooperation with a fixed contact. When such a device is directly connected in a control circuit the contact will permit the interrupting of but a minute quantity of current without damaging the contacts either from arcing at the metal contact, or from oxidizing the surface of the mercury, which in turn ruins the adjustment for fine control of temperature. I have experienced this difliculty in connection with the control of piezo electric crystal oscillators and have devised the circuit disclosed herein that permits the use of a negllgible current flow through the mercury or bi-metallic thermal system to provide a method of accurate temperature control.

In Fig. 1, I haveshown a bi-metallic contact member 1 having parts 1a and lb of different coeflicients of expansion. The bi-metallic member 1 carries a contact 2 at one end thereof that is arranged to close or open an electrical circuit to the adjustable contact member 3 carried by the screw threaded member 4 in the standard 5. I may also employ a mercury expansion member as shown at 12 in Fig. 2 that consists of a glass container with a well of mercury 15 at its base and a capillary tube associated with the well that causes the rise and fall of a fine column of mercury with changes in temperature. A tungsten or iron wire 33 is placed in the well and passes through a glass seal to the exterior of the bulb, and thence to the battery 16. Another tungsten wire 14 is inserted in the capillary tube to provide the make and break contact with the mercury column when under influence of temperature changes. A source of grid biasing voltage is shown at 9 and 16. Connected to the negative end of the battery 9 is a high resistance 8 of a value from 100,000 00 to 500,000 ohms, the opposite terminal of cuit 27 that is coupled to the inductance 30 which is connected direct to the grid 6?) ofinantenna-ground circuit 31. The temperacoil. 19.

the vacuum tube 6. The tube has the cus-. ture control equipment is similar to that tomary filament 6a, heating battery 7, plate shown in Fig. 2.

electrode 60 and the plate battery 11. re- It is therefore apparent that changes in lay is shown at 10 having relay tongue 17 temperature at the piezo electric crystal eleand cooperating contact 18, and functions .to ment 22 will afiect the thermostatic control open the 110 volt supply circuit to the heater system and turn on or off the heater coil 19. The application of my invention to piezo The operation of this. system is as follows: electric crystal controlled transmitters is of When the mercury column has-not risen to extreme importance as constancy of frequency suflicient height in tube 12 to come in contact control can only be maintained while the piezo with the tungsten wire 14, there is impressed electric crystal element remains at a uniform on the grid 66 of the vacuum tube 6 a high temperature. The control system of my innegative potential from battery 9 through revention is extremely accurate, is eiiected by sistor 8 which produces a no-plate-currentminute changes in temperature conditions,

' flow in the relay 10. In this condition the and provides for the piezoelectric crystal elegrid voltage is obtained from the battery 9 adjacent the piezo electric crystal'e'lement. through the high resistance 8. There is no It will be observed that the heater circuit relay is at rest or is in its inactive position ment being subjected to heat, or the heat may ermitting contact 18 that controls the heatbe cut ofit from the container, in accordance mg coil 19 to be closed. This'high negative with variations in temperature immediately voltage drop across the resistance because, is normally closed and will remain so while due to the negative grid potential, there can the tem erature is below a predetermined be no idcurrent, consequently the full voltlimit. owever, when the temperature rises age 0 the battery 9 is delivered to the grid beyond the limit, the heater coil is cut off to 6b. When the mercury column rises and be connected again when the temperature has I makes contact with the tungsten wire 14, the dropped below the selected limit. Suitable potential of the grid 6bwith respect to the means'may be provided for selectively adjustfilament 6a is changed to zero or to a positive ing the predetermined limit. potential according to the location of the con- While I have described my invention in tactor 34 on battery 16. The application of certain. of its preferred embodiments, I dethe positive potential to the grid 66 causes sire that it be understood that modifications plate current to flow, thus energizing the remay be made and that no limitations are inlay 10. The relay contacts 17'18 are opened tended other than are imposed by the scope by the magnetic pull of the electromagnet 10 of the appended claims. breaking the circuit through the heater 19. What I claim as new and desire to secure It will be observed from the connections of by Letters Patent of the United States is ,as the circuit that the resistance 8 serves the purfollows: pose of preventing a short circuit of the bat- 1. An electrical control circuit comprising teries 9 and 16 and at the same time, it limits an electron tube having grid, filament and the current fiow through the mercury therplate electrodes, an input circuit included mometer circuit or any other type of tembetween said-grid and filament electrodes,

perature control that may be employed, as for example, the bi-metallic construction of Fig. 1.

an output circuit included between said plate and filament. electrodes, a relay disposed in said output circuit, separate potential sources This type of thermostatic control can be, having a common connection to said filament, used for numerous purposes, among which atemperature controlled switch insaid input may be mentioned the temperature control circuit, means for normally subjecting said required in the manufacture of Rochelle salts, grid electrode to a predetermined bias poten- 1 or for piezo electric crystal controlled devices. tial, said temperature controlled switch being Fig. 3 shows the application of this system operative to connect said-grid electrode to to a piezo electric crystal controlled transthe other of said sources for abruptly changmitter. A piezo electric crystal control eleing the effective bias potential on said grid ment 22 is arranged in a container 21 that electrode under conditions of temperature has the heating unit 19 placed in a sub-comvariation for correspondingly controlling partment 23, thus indirectly applying heat said relay. to the crystal 22. The mercury thermometer 2. An electrical control system comprising control unit 12 is in the same compartment as, an electron tube having grid, filament and the crystal 22. The piezo electric crystal eleplate electrodes, an input circuit including ment 22 is connected in the input circuit of said grid and filament electrodes, an output the oscillator tubes 26 which has choke coil circuit including said plate and filament elec- 24 and battery-25 connected thereacross. The trodes, a relay disposed in said output circuit, output circuit of the oscillator includes the a temperature conrolled switching device, inhigh potential source 28 and the tuned cirdependent sources of potential connected with said device and having'a common connection with said filament, means for normally impressing a negative potential upon said grid electrode from one of said sources of potential, said switching device being responsive to changes in temperature for abruptly impressing a positive potential on said grid electrode from the. other of said sources of potential for controlling the oper: ation of said relay.

3. An electrically cont-rolled circuit comprising an electron tube having grid, filament and plate electrodes, an output circuit con nected between said plate and filament electrodes, a relay included in said output circuit, an input circuit connected between said grid and filament electrodes, to independent sources of potential having a common connection with said filament, a temperature controlled switch in said input circuit, means for normally impressin a negative potential on said grid electrode rom one of said sources for rendering said relay in said output circuit inactive, and a circuit in shunt with said input circuit including the other of said sources of potential, a positive charge upon said grid electrode upon changes in temperature conditions for activating said relay under control of said temperature controlled switch.

4. An electrical control system comprising an electron tube having grid, filament and plate electrodes, an input circuit including said grid and filament electrodes, an output circuit including said plate and filament elec- ALFRED oRoss'LEY.

trodes, a relay disposed in said output circuit,

said input circuit includin a source, of potential connected to normal y impress a negative charge on said grid electrode for render ing said relay in said output circuit inoperatlve, an auxiliary circuit in shunt with said input circuit, said auxiliary circuit including an independent source of potential and a temperature controlled circuit maker and breaker operative upon increases in temperature to close a circuit from said grid electrode to said independent source of potential forabruptly impressing a positive charge on said grid electrode from said independent source of potential for activating said relay in accordance with temperature changes.

5. A piezo electric crystal controlled transmission system comprising an oscillator, a piezo electric crystal member for controlling the operation of said oscillator, a temperature controlled circuit maker and breaker positioned' adjacent said piezo electric crystal member and subject to the same conditions of temperature to which said piezo electric crystal is subjected, a heater coil adjacent said piezo electric crystal member, and an electron tube circuit disposed between said temperature controlled circuit maker and breaker and said heater coil, a grid circuit, a plate circuit, a relay in said plate circuit for controlling said 

